Let's quickly get a handle on how this "immigration" thing started.
In the late middle ages/early Age of Reason some men were becoming very rich and powerful because of their global understanding and the seafaring trade that they carried on. These very rich and powerful men began to compete for trade routes. The need to protect their trade routes, their source of wealth and power, became paramount. So, the rich and powerful created modern nation states in order to socialize the high cost of building navies and armies. (the first instance of "socialism for the rich") As well as "uniting" people to the common task of building those navies, national borders restricted the flow of skills, knowledge, information, and physical resources.
As the oligarchy strengthened its hold on the world they also discovered that national borders also gave them a way to hide their extranational machinations. (Without nations, you can't have offshore accounts, for instance)
Without national borders, you don't have "immigration". We are all humans, sharing one, rather small planet. Dividing us, into Americans, French, Mexicans, etc serves only the goals of the rich and powerful. In spite of the "Rah! Rah! Us!" propaganda we've been fed for generations, national borders hold no benefit for the 99 per cent.